Electrical conductor and method of making the same



00L 22, 1935. H BlENFAl-r AL 2,018,343

ELECTRICAL CONDUCTOR AND METHOD OF MAKING THE SAME Filed 0G12.l 19, 1932N07* FEEEU FRU/1 O/DES 02 arf/Efe Manu conm/NDS (caPPf/a azz/Nc)PART/CLES ffl/([0 MTH //vD/NG Ala-mrs INVENTORS HENRI BIENFAIT AND W.L.ET BY l, ww ATTORNEY Patented Oct. 22, 1935 UNITED STATES vPATENT OFFICEELECTRICAL CONDUCTOR AND METHOD 0F f MAKING THE SAME of DelawareApplication October 19, 1932, Serial No. 638,4'l8 In the NetherlandsOctober 27, 1931 4 Claims.

This invention relates to electrical conductors which comprise a core,preferably non-conducting, and coated with an electrically conductinglayer, and also to the method of providing such layers.

It has been found that the diiculties which may be encountered and whichhave often been encountered, when coating bodies with electricallyconducting layers, may be avoided in a simple and eflicient manner bymaking use of the present invention, according to which a body, forinstance an electric device, is provided for this purpose with anelectrically con-ducting layer, which layer contains an organic bindingagent and in addition a finally divided metal, the surface of which isfree of oxides and other nonconducting metal compounds such that theconductivity is practically not reduced by them. It has turned out thatthe cause of the failure of the efforts made for providing electricallyconducting layers consisting of a binding agent mixed with a. finelydivided metal, must often be ascribed to the fact that the metalspresent in the binding agent either lose their conductivity duringoperation of the devices or do not possess at all this conductivity whenthese finely divided metals are used for this purpose in the form inwhich they are on the market. By means of the invention bodies may beobtained which are provided with electrically conducting layersretaining their conductivity even at high temperatures.

In the drawing forming a part of this application, Figs. 1 and 2illustrate, respectively. longitudinal and transverse cross-sectionalviews ofy a composite electrical conductor, according to one form of theinvention, and Fig. 3 is a view similar zo Fig. 2 showing another formof the invenion.

In Figs. 1 and 2 an electrically conducting layer l is applied onto aninsulating body 2 by mixing a iinely divided metal entirely free ofoxides and other nonconducting compounds with an organic binding agentand by subsequently depositing it on the body, for instance, byspraying. Before being mixed with the binding agent the surface of thenely divided metal may be liberated from oxides and other nonconductingcompounds. However, it is also possible as suggested above to coat ametal, which is not entirely de-v prived from oxides and other compoundsbefore being mixed with the binding agent, with a nobl er metal byadding. a solution of a salt of the latter.

In Fig. 3 an electrically conducting layer 3 containing metal particlesconsisting internally of a second metal which need not be free o oxidesand other metal compounds, is applied onto a nonconductive core member4. It has proved to be advantageous to use silver for the outer metaland to use copper or zinc for the inner metal. particles of copper orzinc are coated with silver, as for example, by silver plating.

The invention which, as stated above, may be more particularly used inelectric devices, for instance in electric discharge tubes, has manyadvantages. In the first place conductive layers are obtained. For thispurpose it is possible to start from finely divided metals mixed withone of the known organic binding agents. Furthermore the electricallyconducting layer may be 15 applied on to the body at room temperature.Due to this the invention has a very important advantage over the knownSchoops method in which heating of the body together with'all drawbacksinherent thereto is unavoidable. Moreover, the 20 method according tothe invention is` much simpler and, as regards the means for carrying itout, cheaper than the methods of the prior art. Furthermore .the layermaybe provided in one operation on bodies consisting of ceramic 25material having a smooth surface, for instance, glass, whereas with themetal spraying method referred to above, a lacquer layer must initiallyY be provided in order that the metal sufficiently adheres. 30

The invention will be more clearly understood by the following exampleswhich describe some methods of providing conductive layers according tothe invention.

25 gr. of copper powder is treated with 25 cc. 55 of water in which mg.of concentrated sulfuric acid is contained. 'Ihe suspension is suckedoff, washed out with alcohol, mixed with 50 cc. of an organic bindingagent consisting of 10 gr. of collodion, 5 gr. of ester gum and 5 gramsof 40 dibutylphthalate, in 100 cc. of a solvent, for instance,amylacetate. The suspension thus obtained is applied on to the body in asuitable manner, for instance, by spraying. In this manner a goodconducting layer is formed on the body. Instead of the above mentionedbinding against good results have been obtained with usual commercialnitro-cellulose lacquers.

i The method according to the invention may also be carried out in thefollowing manner: 25 5o gr. of copper powder is suspended in water, towhich a solution is added containing 25 gr.` of

' silver in form of sodium silver-cyanide. The suspension thusobtainedis sucked off, washed out will! alcohol and ether and dried in a vacuumu In other words, the nely divided 5 desiccator. The powder thusobtained is mixed with 50 cc. of an organic binding agent, as indicatedabove.

After thissuspension has been applied for instance, by spraying on to anonconducting body an admirabily conducting layer is formed, whoseconductivity does practically notl decrease even at high temperatures,and which, moreover, is proof against atmospheric inuences.

The conductivity of the coating made with the pure metal powder preparedaccording to the present invention is very much greater than that of asimilar coating made with commercial metal powder. We have found forexample that a sheet of 10 cm. in length and 1 cm. in width preparedaccording to the present invention possesses a resistance of 5 ohms,Whereas the same sheet of commercial metal powder possesses a resistanceof more than 10,000 ohms.

What we claim is:

1. A composite electrical conductor comprising a solid non-conductingcore member and a uniform firmly adherent coating of high conductivity,said coating comprising nely divided ing a, solid non-conducting coremember and a l0 uniform rmly adherent coating of high conductivity, saidcoating comprising finely divided silver coated zinc particles mixedwith an organic binding agent.

4. The method of producing an electrically l5 conducting coating on asolid non-conducting core member, which consists in suspending finelydivided metal particles in a solution containing silver-cyanide, washingout and drying the suspension, mixing the particles thus obtained with20 an organic binding agent, and then uniformly spraying the mixture onto the core member.

HENRI BIENFAIT. WILLEM LEENDERT CARGLUS VAN ZWET.

